The Effect of Zn2+ Deficiency on Ordered Micro-Regions and Dielectric Properties of Pb(Zn1/3Nb2/3)O3-Based Relaxor Ceramics

Abstract:

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0.85Pb(Zn1/3Nb2/3)O3-0.10BaTiO3-0.05PbTiO3 (abbreviated as PZN-based ceramics
hereafter) ternary system ceramics with Zn2+ deficiency were synthesized by the columbite method.
The effect of deficient Zn2+ on phase structure, ordered micro-region size and dielectric properties
was investigated in detail. The analysis of Raman scattering spectra demonstrated that Zn2+ deficiency
sharply enlarged the ordered micro-region size. Zn2+ deficiency significantly increased the dielectric
constant, and decreased the diffusion degree of phase transition. There is a close correlation between
effective ordered micro-regions size and dielectric properties for the PZN-based ceramics.

Abstract: A lead-free piezoelectric ceramic ternary system based on (Bi0.5Na0.5)TiO3 (BNT)-(Bi0.5
K0.5)TiO3(BKT)-BaTiO3(BT) near the morphotropic phase boundary (MPB) between the tetragonal
and rhombohedral phases has been investigated. The samples were prepared by a conventional
sintering technique. Piezoelectric properties, dielectric properties and microstructures of
BNT-BKT-BT lead-free piezoelectric ceramic were studied. The X-ray diffraction (XRD) patterns
show that the ceramics possess a single-phase perovskite structure. The measurements of
piezoelectric properties reveal that this system has a relatively high piezoelectric performance: the
piezoelectric constant d33 reached to 178pC/N and planar electromechanical coupling factor kp
enhanced to 0.325. The BNT-BKT-BT ternary system ceramics could be well sintered at 11500C with
a high-density ratio of more than 95% of the theoretical density.

Abstract: The nano-sized Ba(Zr0.2Ti0.8)O3 powder was prepared by citrate sol-gel method. The crystal
structure and the particle size of the powder were characterized by XRD. The morphology of calcined
powder and the sintered ceramics was observed by TEM and SEM, respectively. The particle size of the
powders calcined at 600oC is about 10 nm. The dense ceramics can be obtained at sintering temperature of
1220 oC, which is much lower than that of the powder prepared by the conventional solid method. The
effects of Al2O3 additive on the sintering behavior, microstructure and dielectric properties of
Ba(Zr0.2Ti0.8)O3 ceramics were also investigated.

Abstract: Lead-free piezoelectric ceramics lithium sodium potassium niobate (LixNayK1-x-y)NbO3
(LNKN100x/100y) have been synthesized by a conventional solid state process. The effects of MnO2
addition on the properties of (LixNayK1-x-y)NbO3(x=0.06, y=0.5)(LNKN6/50) ceramics were investigated.
It was found that a morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases is
in the composition range 0.05

Abstract: Microstructures and microwave dielectric properties of Ca(Sm0.5Nb0.5)O3 ceramics, prepared by a conventional solid-state reaction method, were systematically investigated by varying calcining temperature, sintering temperature and cooling rate. The XRD result showed that a single Ca(Sm0.5Nb0.5)O3 phase could be synthesized at a calcining temperature of 1200 °C. Optimized combination of microwave dielectric properties of εr = 22.36, Q×f = 18030 GHz and τf = -31.2 ppm/°C was obtained for furnace-cooled Ca(Sm0.5Nb0.5)O3 ceramics sintered at 1550 °C for 4 h. However, some microcracks were found from the microstructures of the furnace-cooled specimens. Further, the Q×f value could be increased by controlling the cooling rate during the sintering process due to the disappearance of microcracks in the final material. With a cooling rate of 2 °C/min, Ca(Sm0.5Nb0.5)O3ceramics exhibited an enhanced Q×f value of 37130 GHz.